This problem is more serious,the system is damaged,only reinstall the system.
这个问题比较严重，系统已损坏，只能重新安装系统。

I have reinstalled the system twice. ... any case just install-driver show this problem... ( two monitor connected)

I have no language,which means that the driver you installed is not compatible with your system,but you also install......
无语，这说明你所安装的驱动与你的系统不兼容，还安装。。。

Strange ... nvidia gtx 980 is compatible with nvidia-driver 375 ...

Oh,I don't know that......
噢，那我不知道了。。。

I found a partial solution ....  If connect one monitor no problem .... if connect the second monitor after login display not recognize resolution and disappear the dde dock

see if there is any error in /var/log/Xorg.0.log

Problem solved .... I changed the monitor's display port to 1.1.... 1.2 causes problem with multi monitor